Low cost patch antenna utilized in wireless lan applications

ABSTRACT

The present invention is a low cost patch antenna utilized in one or more wireless LAN applications that include a patch plate that uses double-sided 30 mil FR4 PCB with ½ oz. copper with a cross-shaped slot disposed on the patch plate and a feeding point and a grounding PCB with a top surface. The RF feeding cable has an outer conductor and an inner conductor that is a 50 ohm 086 RF coaxial cable that is used to feed the low cost patch antenna, a plurality of patch supports that include a plurality of plastic cylinders which are used to support the patch plate and a plastic radome to protect the low cost patch antenna. The low cost patch antennas and patch plates can also be assembled in a plurality of different configurations for different Access Points and MIMO applications.

This application claims priority to U.S. Provisional Application61/426,286 filed on Dec. 22, 2010, the entire disclosure of which isincorporated by reference.

TECHNICAL FIELD & BACKGROUND

Current Internet access points and routers usually utilize a dipoleantenna with a maximum gain of approximately 2 dBi and with a relativelynarrow HPBW (half power beam width) in a vertical plane typically in therange of approximately 20° to 30°. Therefore, the dipole antenna'soperating range is limited and does not have the capability to coverevery corner of a private house or a small business unit for effectiveInternet access.

When a RF-front-end IC is connected to an access point antenna, itspecifically requires that the antenna have a relatively high gain andwide bandwidth and good return loss (i.e. S11 better than −13 dB) sothat when the operating point of one or more RFeIC blocks drifts in acertain range, the RFeIC can still work properly. More specifically,when an output matching circuit for power amplifier (PA) and an inputmatching circuit for a low noise amplifier (LNA), both are connected tothe antenna port, the RFeIC blocks are tuned for their optimumperformance, typically at approximately 50-Ohm impedance. If an antennaS11 is better than a certain level (i.e. −13 dB), performancedegradation of PA and LNA can be negligible, while when S11 isapproximately −5 dB (which is typical for most existing embeddedantennas at the two ends of an operating frequency band), performancedegradation could be relatively very high. In many cases such ascellular phone and other portable applications, since many of aplurality of circuit components are relatively very close to theantenna, and the coupling between the antenna and those components makesthe antenna performance to be degraded significantly, and the returnloss at the two ends of the operating band is usually approximately −5dB, the RFeIC's performance will be degraded. Therefore, the systemperformance of a transceiver will be degraded (i.e., relatively lesstransmitted power and increased noise figure in receiving mode as wellas digital signal quality degradation result in relatively shortercommunication link distance and increased time required for particulardata file transfer which adversely effects a battery current'sconsumption etc.)

For antennas that are connected to RF front-end circuitry and are usedin WLAN applications, there is generally a plurality of criticalrequirements. These requirements include relatively wide bandwidth withgood return loss (to guarantee the RFeIC working properly underdifferent conditions), relatively high gain, and low cost. A patchantenna is known for its relatively high peak gain, but it has adisadvantage that it usually has a relatively narrow bandwidth. Torealize the previously stated requirements, a plurality of techniquescan be applied to the patch antenna. To get a low cost patch antenna,only one patch is used in contrast to a plurality of patches utilized toform the patch antenna. Specifically, to get relatively wide bandwidthand good return loss, cross-shaped slots are cut at the center of thepatch plate. By adjusting the length of cross-shaped slots on the patch,the coupling between the patch and free space can be controlled, andthus the equivalent patch dimension and impedance can be controlled.Therefore, by adjusting the slot length on the patch and the feedingpoint location, a relatively low cost, high gain, wide band antenna withexcellent return loss can be obtained, and no matching circuitry isneeded.

The present invention is a relatively low cost and high performancepatch antenna, which has relatively high gain, wide bandwidth, goodreturn loss and high radiation efficiency. The antenna return loss isbetter than −13 dB across the operating frequency band of 2400-2483.5MHz, and its bandwidth at S11=−10 dB is approximately 150 MHz. Itsmaximum gain is approximately +9 dBi and with radiation efficiencygreater than 90% in HFSS simulation. For a single patch antenna element,its HPBW (Half Power Beam Width) in a horizontal and elevation plane isapproximately in the range of 55 to 70 degrees. Therefore, the antenna'scoverage range of an access point device will be relatively greatlyincreased compared to a conventional dipole antenna. In addition, with aplurality of different embodiments of the antenna, the radiation patternof the antenna will be improved to approach that of an Omni-directionalantenna, and excellent isolation (greater than approximately −32 dB) canbe obtained between any two antenna ports, thus the antenna can be usedfor access point and in MIMO (Multiple-input multiple-output)applications.

The present invention relates to a high performance low cost patchantenna and a plurality of embodiments for WLAN applications. It can beused for any RF-front end circuitry that is utilized in an ISM(Industrial-Scientific-Medical) band. The antenna has a relativelycompact size, excellent return loss, wide bandwidth, high gain and highefficiency, and does not require any matching circuitry. Additionalembodiments of the antenna are provided to show a plurality ofapplications of the antenna.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described by way of exemplary embodiments,but not limitations, illustrated in the accompanying drawings in whichlike references denote similar elements, and in which:

FIG. 1A illustrates a top perspective view of a low cost patch antenna,in accordance with one embodiment of the present invention.

FIG. 1B illustrates a top view of a low cost patch antenna, inaccordance with one embodiment of the present invention.

FIG. 1C illustrates a side view of a low cost patch antenna, inaccordance with one embodiment of the present invention.

FIG. 1D illustrates a graph of a simulated return loss of a low costpatch antenna, in accordance with one embodiment of the presentinvention.

FIG. 1E illustrates a front perspective view of a simulated radiationpattern and peak gain of a patch antenna element, in accordance with oneembodiment of the present invention.

FIG. 2A illustrates a side view of a pair of low cost patch antennas, inaccordance with one embodiment of the present invention.

FIG. 2B illustrates a front perspective view of a simulated radiationpattern and peak gain of a patch antenna element, in accordance with oneembodiment of the present invention.

FIG. 2C illustrates a graph of a simulated return loss from the pair oflow cost patch antennas, in accordance with one embodiment of thepresent invention.

FIG. 3A illustrates a side perspective view of a pair of low cost patchantennas in a back to back configuration, in accordance with oneembodiment of the present invention.

FIG. 3B illustrates a front perspective view of a simulated radiationpattern and peak gain of a patch antenna element, in accordance with oneembodiment of the present invention.

FIG. 3C illustrates a graph of a return loss and isolation of a back toback antenna configuration, in accordance with one embodiment of thepresent invention.

FIG. 4A illustrates a side perspective view of a three antenna set in a120° arrangement, in accordance with one embodiment of the presentinvention.

FIG. 4B illustrates a front perspective view of a simulated radiationpattern and peak gain of a radiation pattern and peak gain of back toback antenna configuration at 2.45 GHz, in accordance with oneembodiment of the present invention.

FIG. 4C illustrates a graph of a return loss and isolation of a returnloss and isolation from the three antenna set, in accordance with oneembodiment of the present invention.

FIG. 5A illustrates a side perspective view of a four antenna set in a90° configuration, in accordance with one embodiment of the presentinvention.

FIG. 5B illustrates a front perspective view of a simulated radiationpattern and peak gain of a radiation pattern and peak gain of 90° fourantennas configuration, in accordance with one embodiment of the presentinvention.

FIG. 5C illustrates a graph of a return and loss isolation of a fourantenna set, in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Various aspects of the illustrative embodiments will be described usingterms commonly employed by those skilled in the art to convey thesubstance of their work to others skilled in the art. However, it willbe apparent to those skilled in the art that the present invention maybe practiced with only some of the described aspects. For purposes ofexplanation, specific numbers, materials and configurations are setforth in order to provide a thorough understanding of the illustrativeembodiments. However, it will be apparent to one skilled in the art thatthe present invention may be practiced without the specific details. Inother instances, well-known features are omitted or simplified in ordernot to obscure the illustrative embodiments.

Various operations will be described as multiple discrete operations, inturn, in a manner that is most helpful in understanding the presentinvention. However, the order of description should not be construed asto imply that these operations are necessarily order dependent. Inparticular, these operations need not be performed in the order ofpresentation.

The phrase “in one embodiment” is used repeatedly. The phrase generallydoes not refer to the same embodiment, however, it may. The terms“comprising”, “having” and “including” are synonymous, unless thecontext dictates otherwise.

FIG. 1A illustrates a top perspective view of a low cost patch antenna100, in accordance with one embodiment of the present invention. FIG. 1Bhas similar elements as the elements described and illustrated in FigureA.

The low cost patch antenna 100 includes a patch plate 110, a groundingPCB 120, a RF feeding cable 130, a plurality of patch supports 140 and aplastic radome 150.

The low cost patch antenna 100 is a low cost high performance 2.45 GHzISM band patch antenna utilized in WLAN applications, especially one ormore access point applications and MIMO applications. The low cost patchantenna 100 has only one patch plate 110 with a cross-shaped slot 112disposed on the patch plate 110. The patch plate 110 is made of PCB,metal or other suitable material with a total thickness of approximately0.8 mm, and the dielectric 114 between the patch plate 110 and thegrounding PCB 120 is air. Both the patch plate 110 and grounding PCB 120use double-sided 30 mil FR4 PCB with ½ oz. copper 116,122. The RFfeeding cable 130 is a 50 ohm 086 RF coaxial cable 132 that is used tofeed the low cost patch antenna 100. The outer conductor 131 of the 086RF coaxial cable 132 is soldered on the top surface 124 of the groundingPCB 120, and the inner conductor 133 is soldered on a soldering point135 on patch plate 110. The plurality of patch supports 140 are made ofTeflon plastic but can be made of any other suitable plastic material.The plastic radome 150 is made of PVC plastic with a dielectric constantof 2.6. The dimensions of the plastic radome 150 are approximately 126mm in length, 92 mm in width and 27.4 mm in height with a thickness of 3mm. The radome 150 can be made of any other suitable plastic materialtoo. The low cost patch antenna 100 is connected to an RF front-endchipset with 50 ohm RF coaxial cable 132, and no additional matchingcircuitry is required for its operation.

FIG. 1B illustrates a top view of a low cost patch antenna 100, inaccordance with one embodiment of the present invention. FIG. 1B hassimilar elements as the elements described and illustrated in FIG. 1A.The low cost patch antenna 100 is fed with a 086 RF coaxial cable 132.The outer conductor 131 of the 086 RF coaxial cable 132 is soldered onthe grounding PCB top surface 124, and the inner conductor 133 of the086 RF coaxial cable 132 is soldered on the patch plate 110. Thesoldering point 135 is approximately 4.5 mm from the edge 116 of thepatch plate 110. The patch supports 140 are a plurality of plasticcylinders 142 with a diameter of approximately 2 mm which are used tosupport the patch plate 110. The plastic cylinders 142 are made ofTeflon plastic, but other plastic or other suitable materials can beused too. The distance between the patch plate 110 top surface 118 tothe plastic Radome 150 inner wall 152 is approximately 3 mm. Thethickness of the plastic Radome 150 is approximately 3 mm.

FIG. 1C illustrates a side view of a low cost patch antenna 100, inaccordance with one embodiment of the present invention. FIG. 1C hassimilar elements as the elements described and illustrated in Figure Aand Figure B. The low cost patch antenna 100 has a relatively compactsize, high gain, high efficiency, wide bandwidth and excellent returnloss, resulting in a low cost and high performance patch antennaelement. Due to wide bandwidth and excellent return loss, high gain andhigh efficiency, the patch antenna element will have a plurality ofextensive applications in a plurality of WLAN applications.

HFSS Simulation Results:

The low cost and high performance patch antenna element 100 for 2.4 GHzISM band (2.4-2.4835 GHz) was designed with HFSS software. The antennadimensions have been optimized until excellent performance (Return loss,bandwidth, peak gain etc.) has been obtained in HFSS simulation. Thepatch plate 110 and grounding PCB 120 use double-sided 30 mil FR4 PCBwith ½ oz. copper 116,122, as previously illustrated in FIG. 1B and FIG.1C. The plastic radome 150 uses 3 mm thickness PVC material, althoughother suitable plastic materials can also be utilized.

FIG. 1D illustrates a graph 160 of a simulated return loss of a low costpatch antenna, in accordance with one embodiment of the presentinvention. The return loss is −12.8 dBi at 2.4 GHz and −14.5 dBi at 2.49GHz.

FIG. 1E illustrates a front perspective view of a simulated radiationpattern 170 and peak gain of a patch antenna element 100, in accordancewith one embodiment of the present invention.

From FIG. 1E it is seen that the maximum radiation direction is alongthe x-axis direction of the graph 160 as illustrated in FIG. 1D. In XZplane (Phi=0 degree) the simulated HPBW is approximately 55 degrees andin XY plane (Theta=90 degrees) the simulated HPBW is approximately 70degrees. A scale 180 is provided that indicates a predetermined dB gainrange total based on the plurality of colors illustrated on thesimulated radiation pattern 170.

FIG. 2A illustrates a side view of a pair of low cost patch antennas200,210, in accordance with one embodiment of the present invention. Theupper patch 200 is stacked horizontally above the lower patch 210forming a horizontal configuration 220. The dimensions of the lowerpatch 210 are 48 mm×48 mm×0.8 mm, and the dimensions of the upper patch200 are 37 mm×37 mm×0.8 mm. The lower patch 210 has a plurality of slots212 disposed on it, but the upper patch 200 does not have any slots. Thedistance between upper patch 200 and lower patch 210 is 6 mm.

FIG. 2B illustrates the simulated radiation pattern 205 and peak gain ofthe pair of low cost patch antennas 200,210. FIG. 2B has similarelements as the elements described and illustrated in FIG. 2A. The peakgain at 2.45 GHz is +8.97 dBi. The peak directivity at 2.45 dGz is +9.00dBi and the radiation efficiency is 99.3% in HFSS simulation. A scale230 is provided that indicates a predetermined dB gain range total basedon the plurality of colors illustrated on the simulated radiationpattern 205.

FIG. 2C illustrates a graph 240 of a simulated return loss from the pairof low cost patch antennas, in accordance with one embodiment of thepresent invention. FIG. 2C shows the simulated return loss from the pairof low cost patch antennas 200,210. The return loss is −15.7 dB at 2.4GHz and −16.7 dB at 0.49 GHz. The simulated radiation pattern and peakgain is shown in FIG. 2A. The peak gain of the low cost patch antenna100 at 2.45 GHz is +8.85 dBi. The peak directivity is +9.03 dBi at 2.45GHz and the radiation efficiency at 2.45 GHz is 96.02% in HFSSsimulation.

From FIG. 1D and FIG. 2C it is shown that when the upper patch 200 ishorizontally stacked on the lower patch 210, the antenna performance isimproved. The bandwidth of the pair of low cost patch antennas 200,210will be improved significantly when the upper patch 200 is added abovethe lower patch 210.

FIG. 3A illustrates a side perspective view of two antenna sets 300 in a180° arrangement (back-to-back configuration) for 2×2 MIMO application,in accordance with one embodiment of the present invention. The twoantenna sets 300 are low cost patch antenna sets previously illustratedand described in FIGS. 1A-1C and include a first antenna set 310 and asecond antenna set 320.

FIG. 3B illustrates a front perspective view of a simulated radiationpattern 340 and peak gain of two antenna sets 300 in a 180° arrangement(back-to-back configuration) for 2×2 MIMO application 330, in accordancewith one embodiment of the present invention.

When two patch antennas are fed equally, the radiation pattern of thethird embodiment 300 is shown in FIG. 3B. When only one patch antenna of310, 320 is fed (or the two patch antennas are fed independently), thepeak gain at 2.45 GHz is +8.85 dBi. When both low cost patch antennasare fed equally with a power splitter (not shown), the combined low costpatch antenna 300 has two maximum radiation directions, thus the peakgain at 2.45 GHz is reduced to +6.73 dBi since radiated energy isdistributed between the two maximum radiations, but the radiationpattern is improved that is good for an access point application.Because of the superb isolation between both low cost patch antennas,the back to back configuration 300 can be suitably used in 2×2 MIMO(Multiple-input and multiple-output) applications as well. A scale 350is provided that indicates a predetermined dB gain range total based onthe plurality of colors illustrated on the simulated radiation pattern340.

FIG. 3C illustrates a graph 360 of a return loss and isolation of a backto back antenna configuration, in accordance with one embodiment of thepresent invention.

The simulated return loss and isolation between the two low cost patchantennas 310 and 320 are shown in FIG. 3C. By adjusting the slot 330length of the patch, the patch antennas 310,320 illustrate a relativelywider bandwidth. The return loss is better than −13 dB in FIG. 3C. Theisolation between the two patch antennas 310 and 320 is greater than −35dB.

FIG. 4A illustrates a side perspective view of three antenna sets 400 ina 120° arrangement 410, in accordance with one embodiment of the presentinvention. The three antenna sets 400 are low cost patch antenna setspreviously illustrated and described in FIGS. 1A-1C and include a firstantenna set 420, a second antenna set 430 and a third antenna set 440.The simulated return loss and isolation between any antenna sets420,430,440 are shown in Graph 7. The return loss is better than −13 dB,and the isolation between any two antenna sets 420,430,440 is betterthan −34 dB.

FIG. 4B illustrates a front perspective view of a simulated radiationpattern 450 and peak gain of a radiation pattern and peak gain of 120°configuration 400 at 2.45 GHz, in accordance with one embodiment of thepresent invention. When the three patch antennas are fed equally, theradiation pattern of the three antenna sets 410 is illustrated in FIG.4B.

When all three antenna sets 420,430,440 are fed equally with a powersplitter (not shown), the antenna arrangement 410 has three maximumradiation directions, thus the peak gain is reduced to +5.27 dBi sinceradiated energy is distributed among three maximum radiations, but theradiation pattern is improved significantly that is suitable for accesspoint applications. Because of the superb isolation between any twoantenna sets 420,430,440, this antenna arrangement 410 can be suitablyused in 3×3 MIMO applications. A scale 460 is provided that indicates apredetermined dB gain range total based on the plurality of colorsillustrated on the simulated radiation pattern 450.

FIG. 4C illustrates a graph 470 of a return loss and isolation of areturn loss and isolation from the three antenna set, in accordance withone embodiment of the present invention. When only one antenna set420,430,340 is fed (or three antennas sets 420,430,440 are fedindependently), the peak gain is +8.85 dBi.

FIG. 5A illustrates a side perspective view of four antenna sets 500 ina 90° configuration 510, in accordance with one embodiment of thepresent invention.

The four antenna sets 500 include a first antenna set 520, a secondantenna set 530, a third antenna set 540 and a fourth antenna set 550.The return loss and isolation between any two antenna sets520,530,540,550 are shown in FIG. 4C. The return loss is greater thanapproximately −12 dB across a range of a 2.4-2.5 GHz frequency band, andthe isolation between any two antenna sets 520,530,540,550 is betterthan approximately −28 dB.

FIG. 5B illustrates a front perspective view of a simulated radiationpattern 560 and peak gain of a radiation pattern and peak gain of 90°four antennas configuration, in accordance with one embodiment of thepresent invention.

When all four antennas are fed equally, the radiation pattern of thefour antenna sets is shown in FIG. 5B. Because of the superb isolationbetween any two antenna sets 520,530,540,550, this antenna configuration510 can be used in 4×4 MIMO (Multiple-input and multiple-output)applications as well as 5××5 MIMO applications. One additional low costpatch antenna can also be disposed on top of this antenna configuration510 to form a 5×5 MIMO application. A scale 570 is provided thatindicates a predetermined dB gain range total based on the plurality ofcolors illustrated on the simulated radiation pattern 560.

FIG. 5C illustrates a graph 570 of a return and loss isolation of a fourantenna set, in accordance with one embodiment of the present invention.When only one antenna set 520,530,540,550 is fed (or four antennas520,530,540,550 are fed independently), the peak gain is +8.85 dBi. Whenall four antennas 520,530,540,550 are fed equally with a power splitter(not shown), the antenna configuration 510 has four maximum radiationdirections, thus the peak gain is reduced to +5.6 dBi since radiatedenergy is distributed among four maximum radiations, but the radiationpattern is improved significantly and is now very close to that of anOmni-directional antenna, and that is suitable for access pointapplications.

While the present invention has been related in terms of the foregoingembodiments, those skilled in the art will recognize that the inventionis not limited to the embodiments described. The present invention canbe practiced with modification and alteration within the spirit andscope of the appended claims. Thus, the description is to be regarded asillustrative instead of restrictive on the present invention.

1. A low cost patch antenna utilized in one or more wireless LANapplications, comprising: a patch plate that uses double-sided 30 milFR4 PCB with ½ oz. copper with a cross-shaped slot disposed on saidpatch plate and a feeding point; a grounding PCB with a top surface; aRF feeding cable with an outer conductor and an inner conductor that isa 50 ohm 086 RF coaxial cable that is used to feed said low cost patchantenna; a plurality of patch supports that include a plurality ofplastic cylinders which are used to support said patch plate; and aplastic radome to protect said low cost patch antenna.
 2. The antennaaccording to claim 1, wherein said cross-shaped slot length can beadjusted to increase bandwidth.
 3. The antenna according to claim 1,wherein said patch plate is made of PCB or metal.
 4. The antennaaccording to claim 1, wherein said patch plate has a total thickness ofapproximately 0.8 mm.
 5. The antenna according to claim 1, wherein saidfeeding point is approximately 4.5 mm from an edge of said patch plate.6. The antenna according to claim 1, wherein an upper patch plate isstacked horizontally above a lower patch plate forming a horizontalconfiguration.
 7. The antenna according to claim 1, wherein a pair ofsaid low cost patch antennas are in a vertical back-to-backconfiguration.
 8. The antenna according to claim 1, wherein saidgrounding PCB uses double-sided 30 mil FR4 PCB with ½ oz. copper.
 9. Theantenna according to claim 1, wherein said outer conductor is solderedon said top surface of said grounding PCB.
 10. The antenna according toclaim 1, wherein said inner conductor is soldered on said feeding pointon said patch plate.
 11. The antenna according to claim 1, wherein saidplastic cylinders are made of Teflon plastic.
 12. The antenna accordingto claim 1, wherein said patch supports have a diameter of approximately2 mm.
 13. The antenna according to claim 1, wherein said plastic radomedimensions are approximately 126 mm in length, 92 mm in width and 27.4mm in height with a thickness of approximately 3 mm.
 14. The antennaaccording to claim 1, wherein said plastic radome is made of PVC plasticwith a dielectric constant of approximately 2.6.
 15. The antennaaccording to claim 1, wherein said low cost patch antenna is a low costhigh performance 2.4 GHz ISM band patch antenna utilized in said WLANapplications.
 16. The antenna according to claim 1, wherein said lowcost patch antenna is utilized in one or more access point applicationsor utilized in one or more MIMO applications.
 17. The antenna accordingto claim 1, wherein said low cost patch antenna is connected to an RFfront-end chipset with said 50 ohm RF coaxial cable.
 18. The antennaaccording to claim 1, wherein three said low cost patch antenna set areset in a 120° arrangement.
 19. The antenna according to claim 1, whereinfour said low cost patch antenna sets are set in a 90° arrangement. 20.The antenna according to claim 19, wherein one additional said low costpatch antenna is disposed on top of said four low cost patch antennasets to form a 5×5 MIMO application.